Hot gas defrost refrigerating system and valve means therefor



May 12, 1964 F. A. SCHUMACHER HOT GAS DEFROST REFRIGERATING SYSTEM ANDVALVE MEANS Tl-IEREFOR Filed Sept. 21, 1962 F'IGJ y 6 LL---=IL-JL JFIG.5'

INVEN'IOR. FRANK A. scuuumuza ms A'Fb RNEY United States Patent3,132,491 HGT GAS DEFROST REFRIGERATING SYSTEM AND VALVE MEANS THEREFORFrank A. Schnmacher, Louisville, Ky., assignor to General ElectricCompany, a corporation of New Yuri: Filed Sept. 21, 1962, 501'. No.225,321 7 Claims. (Q1. 62-473) This application is acontinuation-in-part of my copending application Serial No. 155,604,filed November 29, 1961, now abandoned, and assigned to the sameassignee as the present invention.

This invention relates to refrigeration systems and is more particularlyconcerned with an improved valve means for periodically directing theflow of hot compressed refrigerant to the evaporator for defrostingpurposes and simultaneously restricting the return flow of refrigerantfrom the evaporator to the compressor component of the system.

During normal or refrigerating operation of a refrigerating systemincluding a compressor, a condenser, a flow restrictor, an evaporatorand a suction line connected in closed series connection, frost tends tocollect on the evaporator component of the system. A known means forremoving this frost layer by warming the evaporator to defrostingtemperatures comprises the periodic introduction of hot compressedrefrigerant from the high pressure side of the system directly into theevaporator Where it condenses and warms the evaporator to defrostingtemperatures. The present invention is generally concerned with arefrigerating system of this type including improved flow control meansfor controlling the flow of refrigerant during the defrost operation ofthe system.

It is an object of the present invention to provide a hot gas defrostingrefrigerating system including an improved valve means for controllingand modifying the flow of refrigerant through the system during defrostoperation thereof.

Another object of the invention is to provide a unitary valve meansadapted to automatically restrict the return flow of refrigerant fromthe evaporator to the compre sor during the period that hot compressedrefrigerant is being introduced into the evaporator for defrostpurposes.

A further object of the invention is to provide a simple and reliableflow control valve for a hot gas defrost refrigerating system includingmeans for introducing a restriction to the flow of refrigerant from theevaporator to the compressor whenever hot compressed refrigerant isintroduced by operation of the valve into the evaporator component ofthe system and for removing the restriction upon operation of the valveto return the system to normal refrigerating operation.

Further objects and advantages of the invention will become apparent asthe following description proceeds and the features of novelty whichcharacterize the invention will be pointed out with particularity in theclaims annexed to and forming a part of this specification.

In carrying out the objects of the present invention, there is provideda refrigerating circuit including a compressor, a condenser, a flowrestrictor, an evaporator and a suction line connected in closedseries-flow relationship so that during normal or refrigeratingoperation of the system the compressor withdraws low pressurerefrigerant from the evaporator and discharges high pressure orcompressed refrigerant into the condenser where it is condensed beforeflowing through the flow restrictor into the evaporator. For the purposeof periodically warming the evaporator to defrosting temperatures inorder to melt frost accumulated thereon, the system includes a unitaryvalve structure for introducing hot compressed refrigerant directly intothe evaporator and for restricting the flow of refrigerant from theevaporator to the compressor during the defrost operation of the system.In its preferred form, the single or unitary valve provided for thispurpose comprises a cylindrical valve body having an upper high pressureinlet chamber connected to the normal refrigerant circuit between thecompressor and the restrictor and an intermediate outlet chamber havingan outlet connection to the inlet end of the evaporator. The valveincludes a normally closed valve port between these chambers which, whenopen, permits flow of hot compressed refrigerant directly to theevaporator. The valve also includes a suction line chamber at the lowerend thereof having two suction line connections and a movable pistonwhich forms a wall between the intermediate and suction chambers. Uponan increase in pressure in the intermediate chamber resulting fromopening of the valve port, the piston is adapted for movement from anormal position in which the two suction line connections are open tothe suction chamber to a second position in which the piston overliesthe two suction line connections. The valve also includes means forrestricting but not completlcy interrupting the flow of refrigerantthrough the suction line when the piston is in its second position.

For a better understanding of the invention reference may be had to theaccompanying drawing in which:

FIGURE 1 is a diagrammatic illustration of a refrigeration systemembodying the present invention;

FIGURE 2 is a vertical sectional view of one form of valve employed inthe practice of the present invention;

FIGURE 3 is a sectional view of a portion of the valve shown in FIGURE 2with the piston in its suction line restricting position;

FIGURE 4 is an enlarged view of a portion of the valve of the presentinvention illustrating a preferred embodiment thereof, and

FIGURE 5 illustrates a modification of the valve of the presentinvention.

With reference to FIGURE 1 of the accompanying drawing, there isillustrated a refrigerating system including a compressor 1, a condenser12, a capillary flow restrictor 3, an evaporator t, and a suction line 6which are connected in series-flow relationship to form a normalrefrigerating system in which the capi lary flow restrictor 3 maintainsa pressure differential between the condenser and the evaporator suchthat circulating refrigerant will be maintained at condensing pressureswithin the condenser and will vaporize in the evaporator. Gaseousrefrigerant is Withdrawn from the evaporator through the suction line 6by the compressor 1 which compresses the refrigerant and discharges thecompressed refrigerant through a discharge line 8 into the condenser 2.

When a refrigerating system of this type is designed for continuousoperation of the evaporator at subfreezing temperatures, there is agradual accumulation of frost on the evaporator and other lowtemperature components of this system. This frost layer must be removedperiodically in order that the system will operate at maximumefiiciency.

In accordance with the present invention, a single or unitary valve isprovided for both introducing hot compressed refrigerant directly intothe evaporator for defrost purposes and for automatically restrictingthe return flow of refrigerant from the evaporator to the compressorduring defrost operation so as to maintain condensing pressures withinthe evaporator during the defrost period.

This valve, which is generally indicated by the numeral 14 in FIGURE 1of the drawing, is shown in detail in FIGURE 2 of the drawing. In thepreferred form thereof, it comprises a cylindrical valve body 15 havingtherein a plurality of chambers including an upper high pressure chamber16 and an intermediate outlet or low pressure chamber 17. The chambersto and 17 are connected by a valve port 18 which, during normalrefrigerating operation of the system, is closed by a needle valve 19.The high pressure chamber 16 has an inlet connection 2'9 connecting thatchamber to a high pressure portion of the system between the compressor1 and the flow restrictor 3, preferably to the discharge line 8 leadingfrom the compressor 1 to the condenser 2. The chamber 17 has an externalconnection 21 connecting that chamber to the inlet end 9 of theevaporator so that it is normally filled with low pressure refrigerant.When it is desired to defrost the evaporator by introducing hotcompressed refrigerant directly into the evaporator, a solenoid 24surrounding the upper or plunger portion 25 of the valve is energizedcausing the needle valve 19 to lift and open the port 18. Hot compressedrefrigerant can then flow from the compressor through the port 18 anddirectly into the evaporator inlet 9.

In accordance with the present invention, the valve 14 also includesmeans for automatically restricting the flow of refrigerant from theevaporator 4 to the compressor 1 during defrost operation of the system.To this end the valve includes a suction gas chamber 27 at the oppositeor lower end of the valve body from the high pressure chamber 16. Thissuction chamber 27 is connected directly into the suction line 6 andincludes an inlet port or connection 28 for receiving refrigerant fromthe evaporator and an outlet port 29 connected to the compressor intake.A movable piston 39 separates the suction chamber 27 from the chamber 17and the upper face 31 of this piston forms one wall of the low pressurechamber 17. The piston 30 is normally positioned during refrigeratingoperation of the system between the outlet connection 21 and the twosuction line ports or connections 28 and 29. In this position, thepiston permits unrestricted flow of suction gas from the evaporator tothe compressor 1. A spring means 33 serves to bias the piston 30upwardly within the valve body to this normal position and a stop 34- inthe form of a pin afixed to the surface 31 of the piston is adapted toengage the lower surface of the port member 18 to limit the upwardmovement of the piston and thereby prevent the piston from closing thelow pressure chamber outlet 21.

The spring 33 is of a strength such that when the valve port 18 is open,the high pressure refrigerant introduced through that port into thechamber 17 will cause the piston 349 to move downwardly against thebiasing action of spring 33 to a lower position as shown in FIGURE 3 ofthe drawing in which the piston 30 overlies both of the connections 28and 29, or in other words is in the path of the refrigerant suction gasflowing from the evaporator to the compressor through the chamber 27. Acircumferential groove 37 provided in the cylindrical walls of thepiston 30 provides a restricted connection between the inlet and outletconnections or ports 28 and 29 when the piston 31) is in its lowerposition thereby permitting a restricted flow of refrigerant from theevaporator back to the compressor during the defrosting operation. Astop pin 39 provided on the lower face of the piston 36 engages the endcap 40 of the valve to limit the downward travel of the piston andposition the restricting groove 37 in communication with the inlet andoutlet connections 28 and 29.

The groove 37 is designed to provide a restriction such that duringdefrost operation, refrigerant will be returned to the compressor at arate sufficient to maintain proper low and high side pressures in thesystem. Preferably the low side or compressor intake pressure isslightly higher during defrost than during normal operation. The highside pressure, that is, the pressure within the defrosting evaporator,should be suflicient to ensure substantially complete condensation ofthe gaseous refrigerant being supplied to the evaporator.

As has been previously indicated, the valve 14 provides the dualfunction of controlling the flow of high pressure refrigerant throughthe system and of restricting the flow of low pressure refrigerant fromthe evaporator to the compressor during defrost operation of the system.During normal refrigerating operation, the port 18 of the valve 14 isclosed by the needle valve 19 and the refrigerant compressed by thecompressor 1 flows through the condenser 2, the restrictor 3 and intothe evaporator 4 for normal cooling operation of the evaporator.Periodic energization of the solenoid 24 by any suitable defrost controlmeans causes the needle 19 to move upwardly and open the port 13. \Vhenthis pont is opened, there is a preferential flow of warm refrigerantfrom the high pressure side of the system to the evaporator inlet or, inother Words, a refrigerant flow which bypasses the restrictor 3. Thispreferential flow results from the lower flow restric tion offered bythe valve 14 and the associated connections of the chambers 16 and 17 tothe remaining portions of the system as compared with the flowrestriction provided by the flow restrictor 3. Also when the valve port18 is opened, the increase in pressure in the chamber 17 forces thepiston 30 downwardly to insert the restriction 37 into the suction line6. The restriction 37 causes the warm high pressure gaseous refrigerantto condense in the evaporator 4 so that its heat of condensation aids inwarming the evaporator to defrost temperatures.

With the valve port 18 open and the restriction 37 interposed in thesuction line between the evaporator and the compressor, the intermediatechamber 17 as well as the evaporator 4 and the portion of the suctionline up to the suction port 23 is filled with high pressure refrigerant.The suction chamber 27 which is disconnected from the suction ports 28and 29 by the lowered piston is filled with low pressure refrigerant,this chamber 27 being at suction pressure when the piston is first movedto its lower position. During the period that the piston is in its lowerposition, the pressure within the suction chamber 27, due to leakagearound the piston 30, is somewhere between the high upstream pressure atthe port 28 and the low downstream or compressor suction pressure at theport 29 and is generally stabilized at a value which is the mean oraverage of the pressures in the conduit ports 28 and 29. The pressuredifferential across the piston 30, or in other words, the differencebetween the pressures in the chambers 17 and Z7 is suflicient to resistthe biasing action of the compressed spring 33 and hold the piston 30 inits lower or defrost position as long as the valve port 18 is opened.

Operation of the system on the defrost cycle continues until theevaporator has been warmed to defrosting temperatures. At this point,means (not shown) responsive to an above freezing temperature of theevaporator deenergizes the solenoid 24 whereupon the port 18 is againclosed. Closing of the port 18 cuts off the chamber 17 from the highpressure side of the system and results in a lowering of the pressure inthat chamber. As the pressure in the chamber 17 gradually decreases, thecompressed spring 33 moves the piston 30 upwardly towards its normalposition and when the piston finally clears both of the ports 28 and 29,the system is reset for operation on a normal refrigerating cycle.

While the downward travel of the piston at the initiation of defrost isquite fast due to the sudden increase in pressure in the chamber 17, thereturn travel is slower due to the fact that the balance of pressureconditions on the piston including the pressure of the spring thereonmust be reversed before the piston will rise to its normal position. Inother words, in order that the piston return to its normal or upperposition when needle valve 19 is closed at the end of a defrost cycle,it is necessary that the pressure exerted on the piston 30 by therefrigerant in the chamber 27 plus the biasing force of the spring 33 begreater than the pressure exerted on the piston by the refrigerant inchamber 17.

At the end of a defrost cycle, when the needle valve closes port 18 sothat the flow of higher pressure refrigerant into chamber 17 is stopped,the pressure in the chamber 17 tends to become the same as the pressuresnsaasi at the port 28 since the two are connected through theevaporator. Also, since the evaporator is then connected in the systemdownstream from the flow restrictor 3, its pressure and hence thepressure in chamber 17 gradually decreases. These changing conditionsresult in a drop in pressure in the chamber 17 which may cause thepiston to risebut as the spring 33 expands, the force exerted thereby onthe piston diminishes. If the rise is sufficient to cause the lower endof the piston 3i to open communication between the suction chamber 27and both of the ports 28 and 29, the pressure in the chamber 27 willbecome the same as the pressure at the port 28 and hence in the chamber17 so that the spring can then return the piston completely to itsnormal or upper position.

To assure an early and positive equalization of the pressures inchambers 17 and 27 and to avoid any possibility of the chamber 27becoming connected to the lower pressure port 29 before it is connectedto the high pressure port 23 with the result that its pressure dropsrather than increases, the port 28 is preferably offset slightlydownwardly from or lower than the port 29. This construction isillustrated in FIGURE 4 of the drawing in which the piston is shown atone point in its upward travel from its defrost position to its normalposition. While both ports are closed when the piston is in its lower ordefrost position, during rise of the piston following a defrost cycle,the bottom wall of the piston first clears the port 23 and provides aconnection between the port 28 and the suction chamber 27 therebyadmitting to chamber 27 refrigerant at the same pressure as that in port23 and hence in chamber 17. The resultant equalization fluid pressureson the piston 30 then permits the spring 33 to take over and move thepiston completely to its upper position.

Preferably, also the length of that portion of the piston below thegroove 37, that is the distance between the groove and the lower face ofthe piston should be such that the ports 28 and 29 are at all timesinterconnected either below the piston, when the piston is in its upperposition, or through the groove 37 when the piston is in its defrostposition. Otherwise, at some point in the return travel of the piston toits normal position, the piston might completely close off both portsand thereby delay the change in pressure conditions required to restorethe system to normal refrigerating operation.

Various changes in the valve structure can be made without affecting itsoperation. Under some system conditions, how of refrigerant over andthrough the spring 33 has been found to cause a hissing or vibratingnoise in the system. This can be avoided by the modification illustratedin FIGURE of the drawing in which the piston 36 is so designed that noportion of the spring 33 is in the path of the suction gas. In thismodification the piston includes a spring engaging portion 46 forengaging the upper end of the spring 33 and this portion is connected tothe main portion of the piston 30 by a small shaft 47 which spaces thespring engaging portion 46 from the main body of the piston 30 toprovide for unrestricted flow of refrigerant between the ports 28 and 29when the piston is in its upper or normal position. Also instead ofproviding a pin 39 for limiting the downward travel of the piston 30, astop 44 on cap 40 may be used for this purpose and also for the purposeof providing means for mounting the spring 33. Otherwise the operationof the modification illustrated in FIGURE 5 of the drawing is the sameas the operation of that illustrated in FIGURES 2, 3 and 4 of thedrawing.

While there has been shown and described particular embodiments of thepresent invention, it will be seen that the invention is not limitedthereto. For example, while port 23 is preferably offset from port 29 toassure an early increase in the pressure in chamber 27, it will beobvious that the same result can be obtained by notching the lower edgeof port 28 and the adjacent portion of the valve body. It is, therefore,intended by the appended claims to cover all modifications within thespirit and scope of the invention.

What I claim as new and desire to secure by Letters Patent of the UnitedStates is:

LA valve for controlling the flow of refrigerant between the compressorand evaporator components of a refrigerating system, said valvecomprising:

(a) a cylindrical valve body having first, second and third chamberstherein,

(b) said first chamber having an inlet for connection with thecompressor discharge,

(0) said second chamber being disposed between said first and thirdchambers and having an outlet for connection to the inlet end of saidevaporator,

(at) said third chamber having spaced inlet and outlets for connectionrespectively to the outlet end of said evaporator and the compressorintake,

(e) a valve port interconnecting said first and second chambers and avalve member normally closing said valve port and means for moving saidvalve memher to a position in which said port is open,

(7) a piston slidably arranged in said valve body forming a movable walldividing said second and third chambers, said piston being movablebetween a first position providing unrestricted communication betweensaid third chamber inlet and outlet connections and a second position inwhich said piston covers said third chamber inlet and outletconnections,

(g) means providing restricted communication between said third chamberinlet and outlet connections when said piston is in its second position,and

(h) spring means for normally positioning said piston in said firstposition when said valve port is closed by said valve member and forpermitting movement of said piston to its second position upon movementof said valve member to open said valve port to introduce high pressurerefrigerant into said second chamber.

2. A valve for modifying the flow of refrigerant in a refrigeratingsystem including a compressor, a condenser, a restrictor, an evaporatorand a suction line normally connected in closed, series flowrelationship in order to introduce compressed refrigerant from thecompressor directly into the evaporator and automatically restrict thefiow of refrigerant through the suction line, said valve comprising:

(a) a cylindrical valve body, said body including,

(b) an inlet chamber having an inlet for connection to the compressordischarge,

(c) an outlet chamber having an outlet for connection to the inlet endof the evaporator,

(d) a first suction line connection to said evaporator and a secondsuction line connection to said compressor intake, said suction lineconnections being spaced from said outlet,

(e) normally closed valve means between said inlet and outlet chambersand means for opening said valve means, and i (f) a piston in said valvebody forming one wall of said outlet chamber and normally positionedwithin said valve body between said outlet and said suction lineconnections and movable to a second position between said suction lineconnections by an increase in pressure in said outlet chamber when saidvalve means is open, said piston including means defining a restrictedcommunication between said suction line connections when said piston isin said second position.

3. A valve for use in a refrigerating system including a compressor, acondenser, a restrictor, an evaporator and a suction line normallyconnected in closed, series flow relationship to periodically introducecompressed refrigerant from the compressor directly into the evaporatorand simultaneouly restrict the flow of refrigerant through the suctionline, said valve comprising:

(a) a cylindrical valve body, said body including,

(b) an inlet chamber adjacent one end of said body and having an inletfor connection to the compressor discharge,

(c) an outlet chamber intermediate the ends of said valve body andhaving an outlet for connection to the inlet end of the evaporator,

(r!) a first suction line connection to said evaporator and a secondsuction line connection to said compressor intake, said suction lineconnections being adjacent the other end of said valve body and spacedfrom one another,

(e) normally closed valve means between said inlet and outlet chambersand means for opening said valve means,

(1) a piston in said valve body forming one wall of said outlet chamberand normally positioned intermediate said outlet connection and saidsuction line connections, said piston being movable to a second positionbetween said suction line connections by an increase in pressure in saidoutlet chamber when said valve means is open, said piston including anannular groove defining a restricted communication between said suctionline connections when in said second position.

4. A unitary valve for modifying the flow of high pressure refrigerantto the evaporator component of a refrigerating system and automaticallyrestricting the flow of low pressure refrigerant in the system duringthe modified flow, said valve comprising:

(a) a cylindrical valve body including,

(b) a high pressure inlet chamber at the upper end of said body,

() a low pressure chamber at the lower end of said body and havingcircumferentially spaced inlet and outlet ports,

(d) an intermediate outlet chamber,

(e) normally closed valve means between said inlet and outlet chambersand means for opening said valve means,

(1) a movable piston within said valve body between said outlet chamberand low pressure chamber forming one wall of each of said chambers,

(g) means for normally positioning said piston within said valve bodybetween said valve means and said low pressure chamber ports and forpermitting movement of said piston downwardly to a second positionoverlying both of said low pressure ports upon opening of said valvemeans to increase the pressure in said outlet chamber,

(It) means defining a restricted communication between said suction lineports when said piston is in said second position,

(i) said inlet port being lower than said outlet port whereby duringreturn movement of said piston to its normal position said inlet port isconnected to said suction chamber ahead of said outlet port.

5. A valve for modifying the flow of high pressure refrigerant to theevaporator component of a refrigerating system and automaticallyrestricting the flow of low pressure refrigerant in the system duringthe modified fiow, said valve comprising:

(a) a cylindrical valve body including,

(b) a hi h pressure inlet chamber at the upper end of said body,

(0) a low pressure chamber at the lower end of said body and havingcircumferentially spaced inlet and outlet ports,

(at) an intermediate outlet chamber,

(e) normally closed means between said inlet and outlet chambers, andmeans for opening said valve means,

(f) a movable piston within said valve body between said outlet chamberand low pressure chamber forming one wall of each of said chambers,

(g) means for normally positioning said piston within said valve bodybetween said valve means and said low pressure chamber ports and forpermitting movement of said piston downwardly to a second positionoverlying said low pressure ports upon opening of said valve means toincrease the pressure in said outlet chamber,

(h) said piston including a circumferential groove defining a restrictedcommunication between said suction line ports when said piston is insaid second position,

(i) said inlet port being lower than said outlet port whereby duringreturn movement of said piston to its normal position said inlet port isconnected to said suction chamber ahead of said outlet port.

6. A valve for modifying the flow of refrigerant in a refrigeratingsystem including a compressor, a condenser, a restrictor, an evaporatorand a suction line normally connected in closed, series flowrelationship in order to introduce high pressure refrigerant directlyinto the evaporator and automatically restrict the flow of refrigerantthrough the suction line, said valve comprising:

(a) a cylindrical valve body including,

([1) an inlet chamber at one end of said body and having an inlet forhigh pressure refrigerant,

(c) a suction chamber at the other end of said body and having an inletport for connection to said evaporator and an outlet port for connectionto said compressor intake, said outlet port being circumferentiallyspaced from said inlet port,

(d) an intermediate outlet chamber having an outlet for connection tothe inlet end of the evaporator,

(e) valve means between said inlet and outlet chambers, and means foropening said valve means,

(1) a movable piston between said outlet and suction chambers formingone wall of each of said chambers,

g) spring means for normally positioning said piston within said valvebody between said valve means and said suction chamber ports and forpermitting movement of said piston to a second position sealing saidsuction chamber ports from said suction chamber upon an increase inpressure in said outlet chamber,

(h) means defining a restricted communication between said suction lineconnections when said piston is in said second position,

(i) said suction chamber ports being offset from one another so thatduring return movement of said piston to its normal position said inletport is connected tosaid suction chamber ahead of said outlet port.

7. A valve for controlling the fioW of refrigerant between thecompressor and evaporator components of a refrigerating system, saidvalve comprising:

(a) a cylindrical valve body having first, second and third chamberstherein,

(b) said first chamber having an inlet for connection with thecompressor discharge,

(0) said second chamber being disposed between said first and thirdchambers and having an outlet for connection to the inlet end of saidevaporator,

(03) said third chamber having spaced inlet and outlet ports forconnection respectively to the outlet end of said evaporator and thecompressor intake,

(e) a valve port interconnecting said first and second chambers, a valvemember normally closing said valve port, and means for moving said valvemember to a position in which said valve port is open,

(1) a piston slidably arranged in said valve body forming a movable walldividing said second and third chambers and being movable between afirst posi- 9 10 tion providing unrestricted communication betweenReferences Cited in the file of this patent said third chamber inlet andoutlet ports and a sec- UNITED STATES PATENTS end position in which saidpiston covers said thlrd chamber inlet and outlet ports, 1:394900 Hlbnel1921 (g) said piston including an annular groove in the 5 2,372,456Stewart Mal? 27, 1945 side wall thereof providing restricted communica-2,525,560 Pabst 0013- 10, 1950 tion between said third chamber inlet andoutlet 216311441 Sh9maker Mali 1 1953 ports when said piston is in itssecond position, and 2,679,141 PP y 25, 1954 (h) spring means fornormally positioning said pis- 729,069 Collins 3, 1956 ton in said firstposition when said valve port is 10 2,743,587 HubaCkeF y 1956 closed bysaid valve member and for permitting 2,823,691 Chatham 13, 1953 movementof said piston to its second position upon 2981114 Noake? y 9, 1961opening of said valve port to introduce high pres- 3,003,334 Mahallck10, 1961 sure refrigerant into said second chamber, (i) said thirdchamber inlet and outlet ports being off- 15 FOREIGN PATENTS set fromone another so that during return move- 19,025 Germany Oct. 25, 1956ment of said piston to its first position said third 625,685 GreatBritain July 1, 1949 chamber is first connected to said inlet portbefore said third chamber is connected to said outlet port.

2. A VALVE FOR MODIFYING THE FLOW OF REFRIGERANT IN A REFRIGERATINGSYSTEM INCLUDING A COMPRESSOR, A CONDENSER, A RESTRICTOR, AN EVAPORATORAND A SUCTION LINE NORMALLY CONNECTED IN CLOSED, SERIES FLOWRELATIONSHIP IN ORDER TO INTRODUCE COMPRESSED REFRIGERANT FROM THECOMPRESSOR DIRECTLY INTO THE EVAPORATOR AND AUTOMATICALLY RESTRICT THEFLOW OF REFRIGERANT THROUGH THE SUCTION LINE, SAID VALVE COMPRISING: (A)A CYLINDRICAL VALVE BODY, SAID BODY INCLUDING, (B) AN INLET CHAMBERHAVING AN INLET FOR CONNECTION TO THE COMPRESSOR DISCHARGE, (C) ANOUTLET CHAMBER HAVING AN OUTLET FOR CONNECTION TO THE INLET END OF THEEVAPORATOR, (D) A FIRST SUCTION LINE CONNECTION TO SAID EVAPORATOR AND ASECOND SUCTION LINE CONNECTION TO SAID COMPRESSOR INTAKE, SAID SUCTIONLINE CONNECTIONS BEING SPACED FROM SAID OUTLET, (E) NORMALLY CLOSEDVALVE MEANS BETWEEN SAID INLET AND OUTLET CHAMBERS AND MEANS FOR OPENINGSAID VALVE MEANS, AND (F) A PISTON IN SAID VALVE BODY FORMING ONE WALLOF SAID OUTLET CHAMBER AND NORMALLY POSITIONED WITHIN SAID VALVE BODYBETWEEN SAID OUTLET AND SAID SUCTION LINE CONNECTIONS AND MOVABLE TO ASECOND POSITION BETWEEN SAID SUCTION LINE CONNECTIONS BY AN INCREASE INPRESSURE IN SAID OUTLET CHAMBER WHEN SAID VALVE MEANS IS OPEN, SAIDPISTON INCLUDING MEANS DEFINING A RESTRICTED COMMUNICATION BETWEEN SAIDSUCTION LINE CONNECTIONS WHEN SAID PISTON IS IN SAID SECOND POSITION.